Three dimensional memory and methods of forming the same

ABSTRACT

Some embodiments include a memory device and methods of forming the memory device. One such memory device includes a first group of memory cells, each of the memory cells of the first group being formed in a cavity of a first control gate located in one device level of the memory device. The memory device also includes a second group of memory cells, each of the memory cells of the second group being formed in a cavity of a second control gate located in another device level of the memory device. Additional apparatus and methods are described.

BACKGROUND

Non-volatile memory devices such as flash memory devices are used inmany computers and electronic devices to store information. A flashmemory device usually has a write operation to store information (e.g.,data and instruction codes), a read operation to retrieve the storedinformation, and an erase operation to clear information from thememory. As demand for higher density memory device increases,three-dimensional (3D) memory devices have been proposed. An example ofa conventional 3D memory device is described by Jiyoung Kim et al. in anarticle titled “Novel 3-D Structure for Ultra High Density Flash Memorywith Vertical-Array-Transistor (VRAT) and Planarized Integration on thesame Plane (PIPE)”, published in the 2008 Symposium on VLSI. TechnologyDigest of Technical Papers, pages 22-23. Since 3D memory devices arerelatively new, manufacturing these devices can pose fabrication processchallenges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a memory device having a memory arraywith memory cells, according to an embodiment of the invention.

FIG. 2 shows a schematic diagram of a portion of a memory device havingdata lines located below memory cells, according to an embodiment of theinvention.

FIG. 3 shows a three-dimensional view of a portion of the memory deviceof FIG. 2, according to an embodiment of the invention.

FIG. 4 shows a portion of a control gate and a memory cell of the memorydevice of FIG. 3, according to an embodiment of the invention.

FIG. 5 through FIG. 29 show various processes of forming a memory devicehaving data lines located below memory cells, according to an embodimentof the invention.

FIG. 30 shows a schematic diagram of a portion of a memory device havingdata lines located above memory cells, according to an embodiment of theinvention.

FIG. 31 shows a three-dimensional view of a portion of the memory deviceof FIG. 30, according to an embodiment of the invention.

FIG. 32 through FIG. 38 show various processes of forming a memorydevice with data lines located above memory cells, according to anembodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a block diagram of a memory device 100 having a memoryarray 102 with memory cells 110 according to an embodiment of theinvention. Memory cells 110 can be arranged in rows and columns alongwith access lines 123 (e.g., wordlines having signals WL0 through WLM)and lines 124 (e.g., bit lines having signals BL0 through BLN). Memorydevice 100 uses lines 124 and 128 to transfer information within memorycells 110. Memory cells 110 can be physically located in multiple devicelevels such that one group of memory cells 110 can be stacked on one ormore groups of other memory cells 110. Row decoder 132 and columndecoder 134 decode address signals A0 through AX on lines 125 (e.g.,address lines) to determine which memory cells 110 are to be accessed.Row and column level decoders 136 and 138 of row and column decoders 132and 134, respectively, determine which of the multiple device levels ofmemory device 100 that the memory cells 110 to be accessed are located.

A sense amplifier circuit 140 operates to determine the value ofinformation read from memory cells 110 and provide the information inthe form of signals to lines 124 and 128. Sense amplifier circuit 140can also use the signals on lines 124 and 128 to determine the value ofinformation to be written to memory cells 110. Memory device 100 caninclude circuitry 150 to transfer information between memory array 102and lines (e.g., data lines) 126. Signals DQ0 through DQN on lines 126can represent information read from or written into memory cells 110.Lines 126 can include nodes within memory device 100 or nodes (e.g.,pins or solder balls) on a package where memory device 100 resides.Other devices external to memory device 100 (e.g., a memory controlleror a processor) may communicate with memory device 100 through lines125, 126, and 127.

Memory device 100 performs memory operations such as a read operation toread information from memory cells 110 and a write operation (sometimereferred to as a programming operation) to store information into memorycells 110. A memory control unit 118 controls the memory operationsbased on control signals on lines 127. Examples of the control signalson lines 127 include one or more clock signals and other signals toindicate which operation, (e.g., a write or read operation) that memorydevice 100 performs. Other devices external to memory device 100 (e.g.,a processor or a memory controller) may control the values of thecontrol signals on lines 127. Specific values of a combination of thesignals on these lines can produce a command (e.g., a write or readcommand) that causes memory device 100 to perform a corresponding memoryoperation (e.g., a write or read operation).

Each of memory cells 110 can store information representing a value of asingle bit or a value of multiple bits such as two, three, four, orother numbers of bits. For example, each of memory cells 110 can storeinformation representing a binary value “0” or “1” of a single bit. Inanother example, each of memory cells 110 can store informationrepresenting a value of multiple bits, such as one of four possiblevalues “00”, “01”, “10”, and “11” of two bits, one of eight possiblevalues “000”, “001”, “010”, “011”, “100”, “101”, “110” and “111, or oneof other values of other number of multiple bits.

Memory device 100 can receive a supply voltage, including supply voltagesignals Vcc and Vss, on lines 141 and 142, respectively. Supply voltagesignal Vss may operate at a ground potential (e.g., having a value ofapproximately zero volts). Supply voltage signal Vcc may include anexternal voltage supplied to memory device 100 from an external powersource such as a battery or an alternating-current to direct-current(AC-DC) converter circuitry.

Circuitry 150 of memory device 100 can include a select circuit 152 andan input/output (I/O) circuit 116. Select circuit 152 responds tosignals SEL0 through SELn to select the signals on lines 124 and 128that can represent the information read from or written into memorycells 110. Column decoder 134 selectively activates the SEL0 throughSELn signals based on address signals A0 through AX. Select circuit 152selects the signals on lines 124 and 128 to provide communicationbetween memory array 102 and I/O circuit 116 during read and writeoperations.

Memory device 100 can be a non-volatile memory device and memory cells110 can be non-volatile memory cells such that memory cells 110 canretain information stored thereon when power (e.g., Vcc or Vss, or both)is disconnected from memory device 100. For example, memory device 100can be a flash memory device such as a NAND flash or a NOR flash memorydevice, or other kinds of memory devices, such as a variable resistancememory device (e.g., phase change random-access-memory (PCRAM),resistive RAM (RRAM), etc.).

One skilled in the art may recognize that memory device 100 may includeother features that are not shown in FIG. 1, to help focus on theembodiments described herein.

Memory device 100 may include at least one of the memory devices andmemory cells described below with reference to FIG. 2 through FIG. 38.

FIG. 2 shows a schematic diagram of a portion of a memory device 200having data lines 251, 252, and 253 located below memory cells 210, 211,and 212, according to an embodiment of the invention. Memory cells 210,211, and 212 can be grouped into groups, such as a group of memory cells210, a group of memory cells 211, and a group of memory cells 212. Asshown in FIG. 2, the memory cells in each group share the same controlgate, such as control gate 221, 222, or 223 (with associated signalsWL0, WL1, and WL2). The memory cells are coupled in series as strings,such as strings 215 and 216. Each string can include one of the memorycells from different groups and is coupled between one of transistors231 and one of transistors 232.

As shown in FIG. 2, transistors 231 have gates coupled to select lines241, 242, and 243 (with associated signals SGD0, SGD1, and SGD2).Transistors 231 have nodes (e.g., sources) coupled to data lines 251,252, and 253 (with associated signals BL0, BL1, and BL2). Data lines251, 252, and 253 sometimes correspond to bit lines or sense lines of anon-volatile memory device.

Transistors 232 have gates coupled to select lines 261, 262, and 263(with associated signals SGS0, SGS1, and SGS2). Transistors 232 havenodes (e.g., drains) coupled to a common source 270 of memory cellstrings in a non-volatile memory device.

FIG. 2 shows three groups of memory cells with associated componentscoupled to them, as an example. The number of groups of memory cells andtheir associated components (e.g., control gates and data lines) canvary.

Memory device 200 uses control gates 221, 221, and 223 to control accessto memory cells 210, 211, and 212 during a read operation to sense(e.g., read) information stored in memory cells 210, 211, and 212, andduring a write operation to store information into memory cells 210,211, and 212. Memory device 200 uses data lines 251, 252, and 253 totransfer the information read from these memory cells during a readoperation.

Transistors 231 and 232 are responsive to signals SGD0, SGD1, and SGD2,and signals SGS0, GS1, and SGS2, respectively, to selectively couple thememory cells to data lines 251, 252, and 253 and common source 270during a read or write operation.

To help focus on the description herein; the description herein omitsdetailed description of operations of memory device, such as write,read, and erase operation. One skill in the art would recognize theseoperations. For example, in an erase operation of memory device 200, avoltage of approximately 20 volts can be applied to data lines 251, 252,and 253 while control gates 221, 221, and 223, select lines 241, 242,and 243, and select lines 261, 262, and 263 can be “floated” (e.g.,leave unconnected to a voltage). In this erase operation, electrons frommemory elements of memory cells 210, 211, and 212 may move to data lines251, 253, and 253.

FIG. 3 shows a 3D view of a portion of memory device 200, according toan embodiment of the invention. FIG. 3 also shows X, Y, and Zdirections, and device levels 301, 302, and 303 arranged in theZ-direction. Memory cells 210 of the same group can be arranged in rowsand columns in the X-direction and Y-direction. Each group of memorycells is located in different device levels 301, 302, or 303. Forexample, the group having memory cells 210 is located in device level301. The group having memory cells 211 is located in device level 302.The group having memory cells 212 is located in device level 303.

As shown in FIG. 3, memory cells 210, 211, and 212 in each string (e.g.,memory cells between transistors 231 and 232) are substantiallyvertically aligned in the Z-direction with respect to a substrateunderneath data lines 251, 252, and 253. The substrate is not shown inFIG. 3, but can be similar to substrate 503 of FIG. 5 and FIG. 6. FIG. 3also shows a channel 241 and a conductive material portion 242 extendingvertically in the Z-direction and through memory element 430 of memorycells 210, 211, and 212 in the same string between transistors 231 and232, which corresponds to transistors 231 and 232 of FIG. 2. As shown inFIG. 3, transistor 231 can include a double-gate coupled to a body 391(e.g., transistor channel) to control (turn on or off) the transistor.The structure of the double-gate can include two segments of the sameselect line 241 (as shown in FIG. 3), such that the two segments arelocated on only two respective sides of body 391.

Memory device 200 in FIG. 3 also can include contacts 329, 349, and 359.Contacts 329 provide electrical connections to control gates 221, 222,and 223. Contacts 349 provide electrical connections to select lines241, 242, 243, and 244. Contacts 359 provide electrical connections toand from data lines 251, 252, and 253. Select line 244 and the memorycell associated with it in the Z-direction are not shown in FIG. 2.

FIG. 4 shows a portion of control gate 221 and a memory cell 210 ofmemory device 200 of FIG. 3. Control gates 222 and 223 and memory cells211 and 212 of FIG. 2 have structures similar to control gate 221 andmemory cell 210, respectively. As shown in FIG. 4, control gate 221 caninclude a homogenous material with cavities 420, each cavity being filedwith various components, including materials different from thehomogenous material. The various components include: a memory element430; a channel 441, a conductive material portion 442, and dielectrics421 and 427. Dielectric 421 can include multiple materials 422, 423, and424 arranged as different layers. As shown in FIG. 4, memory element 430of each memory cell 210 has a ring shape (e.g., donut shape) with aninner side 451 and an outer side 452. Each of the other memory cells 211and 212 shown in FIG. 3 also has a ring shape. As shown in FIG. 3,within memory cells 210, 211, and 212 in the same string (e.g., betweentransistors 231 and 232), the entire ring-shape memory element 430 ofeach memory cell is substantially vertically aligned (in theZ-direction) with the entire ring-shape memory element of each of theother memory cells in the same string.

Each memory element 430 can store information, such as based on theamount of charge (e.g., number of electrons) therein. In each suchmemory element 430, the amount of charge corresponds to the value ofinformation store that memory element. The amount of charge can becontrolled in a write operation or in erase operation. For example,electrons from channel 441 or conductive material portion 442, or both,can move to memory element 430 during a write operation due to atunneling effect known to those skilled in the art. In an eraseoperation, electrons from memory element 430 can move back to channel441 or conductive material portion 442, or both, to data lines 251, 253,and 253 (FIG. 2 and FIG. 3). Alternative embodiments might use a memoryelement 430 that can store information, such as based on the resistanceof the element 430, for example.

Memory device 200 of FIG. 3 can be formed using processes similar to oridentical to those described below with reference to FIG. 5 through FIG.29.

FIG. 5 through FIG. 29 show various processes of forming a memory device500 having data lines located below memory cells, according to anembodiment of the invention. Memory device 500 (shown in more details inFIG. 29) can correspond to memory device 300 of FIG. 3.

FIG. 5 shows memory device 500 having a substrate 503, which can includematerials 501 and 502 arranged as layers. Material 501 can include bulksilicon or could be another semiconductor material. Material 502 can bea dielectric material, for example, silicon oxide. FIG. 5 also showsmaterials 504 and 505 formed over substrate 503. Forming materials 504and 505 can include depositing a conductive material over substrate 503and then depositing another conductive material over material 504.Material 504 can include a metal or other conductive materials. Material505 can include undoped polysilicon or doped polysilicon, such as p-typesilicon or another conductive materials.

FIG. 5 also shows an X-direction, a Y-direction perpendicular to theX-direction, and a Z-direction perpendicular to both the X-direction andthe Y-direction. As shown in FIG. 5, materials 504 and 505 can be formedas different layers, one layer over (e.g., on) one or more other layersin the Z-direction.

As used herein, the term “on” used with respect to two or morematerials, one “on” the other, means at least some contact between thematerials, while “over” or “overlaying” could refer to either a materialbeing “on” another material or where there is one or more additionalintervening materials between the materials (e.g., contact is notnecessarily required). The term “on”, “over”, or “overlying” does notimply any directionality as used herein unless otherwise explicitlystated as such.

FIG. 6 shows memory device 500 after data lines 651, 652, and 653 anddevice structures 605 have been formed. A process such as etching (e.g.,dry etching) can be used to remove portions of materials 504 and 505(FIG. 5) to form trenches 511 and 512, which have trench bottoms atmaterial 502. Each of data lines 651, 652, and 653 and each of devicestructures 605 has a greater dimension (e.g., length) extending in theX-direction. A mask (not shown in FIG. 6) having separate openingsextending in the X-direction can be used to form trenches 511 and 512.As shown in FIG. 6, trenches 511 and 512 divide material 504 (FIG. 5)into separate data lines 651, 652, and 653, which can correspond to datalines 251, 252, and 253 of FIG. 2.

FIG. 7 shows memory device 500 after pillars 705 have been formed inarea 701 of memory device 500. Pillars 705 are not formed in area 702 ofmemory device 500. For simplicity, FIG. 7 through FIG. 29 do not showsubstrate 503 of FIG. 6. In FIG. 7, a process such as etching (e.g., dryetch) can be used to remove portions of device structures 605 to formtrenches 711, 712, and 713 in the Y-direction, perpendicular to trenches511 and 512, such that pillars 705 can be formed as shown in FIG. 7. Amask (not shown in FIG. 7) having separate openings extending in theY-direction can be used to form trenches 711, 712, and 713. Each pillar705 can include a height in the Z-direction of approximately 20 to 50nanometers. As shown in FIG. 7, pillars 705 are arranged in rows andcolumns (e.g., in a matrix) in the X-direction and Y-direction. Forsimplicity, FIG. 7 does not show a dielectric material filled intrenches 511 and 512. However, forming memory device 500 in FIG. 7 alsocan include forming a dielectric material (e.g., silicon oxide) to filltrenches 511 and 512 up to a top surface 715 of device structure 605.

FIG. 8 shows memory device 500 after dielectric 831 and select lines841, 842, 843, and 844 have been formed. Select lines 841, 842, 843, and844 can correspond to select lines 241, 242, 243, and 244, respectively,of FIG. 3. In FIG. 8, dielectrics 831 are formed to electrically isolateselect lines 841, 842, 843, and 844 from pillars 705. Dielectrics 831can be formed by, for example, depositing a dielectric material (e.g.,silicon oxide) on at least two sides of each pillar 705 or by oxidizingpillars 705. After dielectrics 831 are formed, select lines 841, 842,843, and 844 can be formed by, for example, depositing a conductivematerial over pillars 705 and trenches 711, 712, and 713 (FIG. 7) andthen removing (e.g., etching) a portion of the conductive material toform select lines 841, 842, 843, and 844 having the structure shown inFIG. 8. Examples of the conductive materials for select lines 841, 842,843, and 844 include polysilicon, metal, or other conductive materials,such as TiN and TaN.

FIG. 8 also shows doped regions 833, which can be formed by inserting(e.g., implanting) n-type impurities into selective portions of devicestructure 605. Examples of n-type impurities include elements such asphosphorus (P) or arsenic (As). The remaining portion of devicestructures 605 that has not been inserted with n-type impurities maymaintain its original material, such as p-type silicon, as describedabove with reference to FIG. 5.

FIG. 9 shows memory device 500 with select lines 941, 942, 943, and 944,which are alternative structures for select lines 841, 842, 843, and 844of FIG. 8. In FIG. 8, opposite sides of each pillar 705 are associatedwith two different segments of the same select line 841, 842, 843, or844. In FIG. 9, except for the top surfaces of pillars 705, each pillar705 can be completely surrounded by the material of one of the selectline 941, 942, 943, or 944 (e.g., four sides of each pillar 705 areassociated with four different segments of the same select line). Higherefficient memory device may be achieved with select lines 941, 942, 943,and 944 in comparison to select lines 841, 842, 843, and 844. Selectlines 941, 942, 943, and 944 can also be alternative structures forselect lines 241, 242, 243, and 244, respectively, of FIG. 3. Thus, eachtransistor 231 of FIG. 2 and FIG. 3 can include a surrounded gate with astructure shown in FIG. 9. Thus, instead of a double-gate shown in FIG.3, each transistor 231 of FIG. 3 can alternatively include a surroundedgate having four different segments of the same select line (such asselect line 941) surrounding body 391 (FIG. 3).

FIG. 10 shows memory device 500 after materials 1001 through 1007 areformed over pillars 705 and select lines 841, 842, 843, and 844.Materials 1001 through 1007 can be formed in both areas 701 and 702 ofmemory device 500. However, to focus on the description herein, FIG. 10does not show some portions of materials 1001 through 1007 in area 702.The description below with reference to FIG. 28 and FIG. 29 describesforming additional components (e.g., components similar to contacts 329of FIG. 3) in area 702 of memory device 500.

In FIG. 10 through FIG. 29, for simplicity, some number designationsassociated with some components of memory device 500 may not be repeatedfrom one figure to another figure. In FIG. 10, before forming materials1001 through 1007, a dielectric material (not shown in FIG. 10), such assilicon oxide, can be formed to fill gaps 1041, 1042, and 1043. Formingmaterials 1001 through 1007 can include alternately depositingdielectric material and conductive material in an interleave fashion,such that these materials are alternately stacked over each other in theZ-direction, as shown in FIG. 10. Materials 1001, 1003, 1005, and 1007can include dielectric materials, such as silicon oxide. Materials 1002,1004, and 1006 can include conductive materials, such as metal orpolysilicon (e.g., n-type silicon for p-type silicon). As shown in FIG.10, materials 1001 through 1007 are formed such that materials 1002,1004, and 1006 are electrically isolated from each other by materials1001, 1003, 1005, and 1007.

FIG. 11 shows memory device 500 after openings (e.g., holes) 1101 havebeen formed in material 1002 through 1107. Holes 1101 are formed suchthat each hole 1101 can be aligned substantially directly over acorresponding pillar 705, as illustrated in FIG. 11. Forming holes 1101can include removing (e.g., etching) a portion of each of materials 1002through 1007, stopping at material 1001, such that at least a portion ofmaterial 1001 or the entire material 1001 remains to separate holes 1101from pillars 705. Forming holes 1101 results in forming cavities 1110 ineach of materials 1003, 1005, and 1007, and cavities 1120 in each ofmaterials 1002, 1004, and 1006. As shown in FIG. 12, cavities 1110 inthe materials 1003, 1005, and 1007 are substantially aligned directlyover cavities 1120 in the other materials 1002, 1004, and 1006. Eachcavity 1110 and each cavity 1120 may have substantially the samediameter, D1. Diameter D1 can also be considered the diameter of eachhole 1101 at the location of each cavity 1110 and each cavity 1120.

FIG. 12 shows memory device 500 after cavities 1220 have been formed inmaterials 1002, 1004, and 1006 (used to form control gates 1221, 1222,and 1223). Forming cavities 1220 can include enlarging the size ofcavities 1120 (FIG. 11) while keeping the size of cavities 1110substantially unchanged (e.g., remaining substantially at diameter D1).For example, enlarging the size of cavities 1120 (FIG. 11) can includeselectively removing (e.g., selective wet or dry etching) a portion ofeach of materials 1002, 1004, and 1006 at each cavity 1120 (FIG. 11)such that the diameter of each cavity 1220 increases to substantiallydiameter D2, while the diameter D1 at each cavity 1110 remainssubstantially unchanged. Diameter D2 is greater than diameter D1.Forming cavities 1120 in materials 1002, 1004, and 1006 also formcontrol gates 1221, 1222, and 1223, which can correspond to controlgates control gates 221, 222, and 223 of FIG. 2.

FIG. 13 shows more details of control gate 1221 of FIG. 12. Controlgates 1222 and 1223 of FIG. 12 have a similar structure as control gate1221. As shown in FIG. 13, control gate 1221 can include a homogenousmaterial with cavities 1220 of FIG. 11 being arranged in rows andcolumns in the X-direction and Y-direction. Each cavity 1220 can includea sidewall 1225.

FIG. 14 and FIG. 15 shows memory device 500 after dielectrics 1421 andmemory elements 1430 have been formed in cavities 1220. For simplicity,FIG. 15 does not show dielectrics 1421 and memory elements 1430 in allcavities 1220. Each dielectric 1421 can be formed on sidewall 1225, suchthat each dielectric 1421 and can be located between the material ofcontrol gate 1221 and memory element 1430, and such that memory element1430 can be electrically isolated from the material of control gate 1221by at least a portion of dielectric 1421. Forming dielectric 1421 caninclude forming multiple materials 1422, 1423, and 1424 (FIG. 15) atdifferent times, one material after another. Forming material 1422 caninclude oxidizing a portion (e.g., a surface) of sidewall 1225 to formdielectric material (e.g., silicon oxide) on sidewall 1225.Alternatively, forming material 1422 can include depositing dielectricmaterial (e.g., silicon oxide) on sidewall 1225. Forming material 1423can include depositing dielectric material (e.g., silicon nitride) onmaterial 1422, wherein a portion of that dielectric material may alsoform on sidewall 1425 of each cavity 1110. Forming material 1424 caninclude depositing dielectric material (e.g., silicon oxide) on material1423.

Memory elements 1430 can be formed after dielectrics 1421 are formed. Asshown in FIG. 15, each memory element 1430 has a ring shape (e.g., adonut shape) with an inner side 1451 and an outer side 1452 of FIG. 14.Forming memory elements 1430 can include depositing a material in holes1101. Since cavities 1220 of FIG. 14 are substantially aligned withcavities 1110, the material (that forms memory element 1430) may fillboth cavities 1110 and 1120. Then, a portion (e.g., center portion ineach hole) of the material that forms memory elements 1430 can beremoved (e.g., by etching in the same, single, etching step) such thatthe material in cavities 1110 can be removed (e.g., completely removed)and the material in cavities 1220 is not completely removed butpartially removed. As shown in FIG. 14, after the material that formsmemory elements 1430 is removed from cavities 1110, a portion ofdielectric material 1423 (e.g., silicon nitride, that was formed onmaterial 1422) may be exposed. As shown in FIG. 14, after the materialthat forms memory elements 1430 is partially removed from cavities 1220,memory element 1430 (formed by the remaining material in a cavity 1220)associated with the same hole 1101 may have its inner side 1451substantially aligned with sidewall 1425 (or sidewall 1425 with portionsof materials 1422 and 1423 of cavities 1110) of cavities 1110.

The material of memory elements 1430 can include, for example,semiconductor material (e.g., polysilicon), dielectric charge trappingmaterial, such as silicon nitride or other dielectric charge trappingmaterials, or a variable resistance material, such as a phase changematerial (e.g., GST). During removing (e.g., etching) a portion of thematerial that forms memory elements 1430, portions 1401 of material 1001located over pillars 705 can also be removed to reduce the thickness ofportions 1401.

FIG. 16 and FIG. 17 show memory device 500 after dielectric 1627 hasbeen formed on inner side 1451 of memory element 1430 and in cavities1110. Forming dielectric 1627 can include depositing dielectric material(e.g., silicon oxide) on inner side 1451. Alternatively, formingdielectric 1627 can include oxidizing a portion (e.g., inner side 1451)of memory element 1430. Forming dielectric 1627 (e.g., by oxidation) mayalso consume material 1423 (FIG. 14) formed on material 1422, whichformed on sidewall 1425 of cavities 1110. Thus, dielectric 1627 may alsoform in cavities over material 1422.

FIG. 18 and FIG. 19 show memory device 500 after channels 1841 have beenformed on dielectrics 1627 in both cavities 1110 and 1220. Formingchannels 1841 can include depositing a conductive material ondielectrics 1627. An etching process can be used to reduce the thicknessof the conductive material after it is deposited. The conductivematerial of channels 1841 can include doped polysilicon, which can havethe same material type (e.g., p-type) as pillars 705. FIG. 18 also showsa formation of openings 1801, which can be formed by removing (e.g., byetching) portions 1401 (FIG. 14) located over pillars 705. As shown inFIG. 19, channel 1841 is facing memory elements 1430 and is electricallyisolated from memory element 1430 by at least a portion of dielectric1627.

FIG. 20 shows memory device 500 after a conductive material 2001 hasbeen formed by, for example, depositing undoped or lightly dopedpolysilicon to place channels 1841 in electrical communication withpillars 705. As shown in FIG. 20, conductive material 2001 forms acontinuous conductive path between channels 1841 and data lines 651,652, and 653 through pillars 705.

FIG. 21 shows memory device 500 after dielectric material 2101 (e.g.,silicon oxide) has been formed over conductive material 2001.

FIG. 22 shows memory device 500 after a formation of openings (e.g.,holes 2201), a conductive material portion 2260, and conductive materialportions 2241. Holes 2201 are formed such that each hole 2201 can bealigned substantially directly over channels 1841, as illustrated inFIG. 22. Forming holes 2201 can include removing (e.g., etching) aportion of dielectric material 2101 and a portion of conductive material2001 (FIG. 21), stopping at a location in material 1007. Holes 2201 canbe formed such that after a portion of conductive material 2001 isremoved during the formation of holes 2201, conductive material 2001 isseparated into conductive material portion 2260 and conductive materialportions 2241, as illustrated in FIG. 22.

FIG. 23 shows memory device 500 after doped regions 2301 have beenformed. Forming doped regions 2301 can include inserting (e.g.,implanting) n-type impurities into top parts of conductive materialportions 2241. Doped regions 2301 can provide a relatively lowresistance connection between channels 1841 and other components ofmemory device 500.

FIG. 24 shows memory device 500 after dielectrics 2401 and channels 2402have been formed. Dielectrics 2401 (e.g., silicon oxide) is formed onsidewalls of conductive material portion 2260 at the location of holes2201. Channels 2402 are formed on sidewalls of dielectric material 2101and on dielectrics 2401.

FIG. 25 shows memory device 500 after conductive material 2501 has beenformed in each of holes 2201, such that channel 2402 can be electricallycoupled to channel 1841 through conductive material 2501, doped region2301, and conductive material portion 2241. Forming conductive material2501 in each of holes 2201 can include depositing a conductive material(e.g., polysilicon) over material, such that the conductive materialfills holes 2201. Then, a top portion of the conductive material can beremoved by, for example, etching back the conductive material or bychemical mechanical planarization (CMP).

FIG. 26 shows memory device 500 after doped regions 2601 and selectlines 2661, 2662, and 2663 have been formed. Forming doped regions 2601can include inserting (e.g., implanting) n-type impurities into topportions of conductive material 2501. Forming select lines 2661, 2662,and 2663 can include removing parts of dielectric material 2101 andconductive material portion 2260 to form trenches 2602, which havetrench bottoms partially extending into material 1007. As shown in FIG.26, trenches 2602 separate conductive material portion 2260 into selectlines 2661, 2662, and 2663, which can correspond to select lines 261,262, and 263 of FIG. 2.

FIG. 27 shows memory device 500 after material 2701 and a common source2770 have been formed. Forming material 2701 can include depositing adielectric material (e.g., silicon dioxide) over material 2101, suchthat the dielectric material fills trenches 2602. Then, a top portion ofthe dielectric material can be removed by, for example, etching back thedielectric material or by CMP. Forming common source 2770 can includedepositing a conductive material (e.g., metal) over materials 2701 and2101.

FIG. 28 shows memory device 500 after materials 1001 through 1007 inarea 702 (FIG. 10) are processed (e.g., by patterning) to form a stairlike pattern with material between the stairs are not shown in FIG. 28.As mentioned above in the description of FIG. 10, some portions ofmaterials 1001 through 1007 are omitted from area 702 of FIG. 10 throughFIG. 27 for clarity. FIG. 28 shows material 1001 through 1007 in area702 after they have been processed to form the stair like pattern. Asshown in FIG. 28, control gates 1221, 1222, and 1223 are formed frommaterials 1002, 1004, and 1006, respectively, which are formed in thestair like pattern.

FIG. 29 shows memory device 500 after contacts 2929, 2949, and 2959 havebeen formed. Contacts 2929 provide electrical connections to controlgates 1221, 1222, and 1223. Contacts 2949 provide electrical connectionsto select lines 841, 842, 843, and 844. Contacts 2959 provide electricalconnections to and from data lines 651, 652, and 653.

As shown in FIG. 29, memory device 500 can include components and memorycells 2910, 2911, and 2912 similar to or identical to components andmemory cells 210, 211, and 212 of memory device 300 described above withreference to FIG. 2 and FIG. 3.

One skilled in the art may readily recognize that additional processesmay be performed to form additional features of a memory device, such asmemory device 500 described above. Thus, to help focus on theembodiments described herein, FIG. 5 through FIG. 29 described above andFIG. 30 through FIG. 38 described below show only some of the featuresof a memory device, such as memory device 500.

FIG. 30 shows a schematic diagram of a portion of a memory device 300having data lines 251, 252, and 253 located above memory cells 210, 211,and 212, according to an embodiment of the invention. Memory device 300can include components similar to those of memory device 200 of FIG. 3.Thus, for simplicity, similar or same components between memory device200 and memory device 3000 are given the same number designations. Thedetailed description of these similar components is not repeated in FIG.30. Main differences between memory device 3000 and memory device 200include the locations of data lines 251, 252, and 253 and common source3070 of memory device 3000 to enable global erase operation. As shown inFIG. 30, data lines 251, 252, and 253 are located above memory cells210, 211, and 212. Common source 3070 is located below memory cells 210,211, and 212 and can couple directly to at least a portion of asubstrate of memory device 3000 (e.g., substrate 3101 in FIG. 31). Thismain difference may allow voltages to be applied to various componentsof memory device 3000 in a different way during an erase operation andmemory device 3000 function differently (e.g., during the global eraseoperation) in comparison with the erase operation (e.g., local eraseoperation) of memory device 200. For example, in an erase operation ofmemory device 3000, a voltage of approximately 20 volts can be appliedto common source 3070, while control gates 221, 221, and 223, data lines251, 252, and 253, select lines 241, 242, and 243, and select lines 261,262, and 26 can be “floated”. In this erase operation, electrons frommemory elements of memory cells 210, 211, and 212 may move (e.g., bytunneling) to common source 3070 (e.g., global erase). In memory 200, asdescribed above with reference to FIG. 2, FIG. 3, and FIG. 4, during anerase operation, electrons from memory elements of memory cells 210,211, and 212 may move to data lines 251, 253, and 253 (e.g., localerase)

FIG. 31 shows a 3D view of a portion of the memory device 3000 of FIG.30, according to an embodiment of the invention. As shown in FIG. 31,data lines 251, 252, and 253 are located above memory cells 210, 211,and 212, common source 3070 is located below memory cells 210, 211, and212 and is coupled to a substrate 3101. Substrate 3101 can includesemiconductor material, such as p-type silicon.

As shown in FIG. 31, memory cells 210, 211, and 212 in each string(e.g., memory cells between transistors 231 and 232) are substantiallyvertically aligned in the Z-direction with respect to substrate 3101.Transistor 232 can include a double-gate or surrounded gate similar tothe double-gate (FIG. 3) or surrounded gate (FIG. 9) of transistor 231of FIG. 3. FIG. 31 also shows a channel 441 and a conductive materialportion 442 extending vertically in the Z-direction and through memoryelement 430 of memory cells 210, 211, and 212 in the same string betweentransistors 231 and 232, which corresponds to transistors 231 and 232 ofFIG. 30.

Memory element 430 in each of memory cells 210, 211, and 212 has a ringshape. As shown in FIG. 31, within memory cells 210, 211, and 212 in thesame string, the entire ring-shape memory element 430 of each memorycell is substantially vertically aligned (in the Z-direction) with theentire ring-shape memory element of each of the other memory cells inthe same string.

FIG. 32 through FIG. 38 show various processes of forming a memorydevice 3200 having data lines located above memory cells, according toan embodiment of the invention. Memory device 3200 (shown in moredetails in FIG. 38) can correspond to memory device 3000 of FIG. 31.

FIG. 32 shows memory device 3200 having a substrate 3201 and trenches3211, 3212, and 3213, and substrate portions 3270 and 3271 formed on atop portion of substrate 3201. Substrate 3201 can include semiconductormaterial, such as bulk silicon. Top substrate portions 3270 and 3271 canbe formed by inserting (e.g., implanting) p-type impurities into a topportion of substrate 3201. Thus, substrate portions 3270 and 3271 caninclude p-type silicon. Forming trenches 3211, 3212, and 3213 andsubstrate portion 3270 can include removing (e.g., etching) a portion ofsubstrate portion 3271. During a write or read operation of memorydevice 3200, substrate portion 3270 can be coupled to a potential, suchas to ground. During an erase operation of memory device 3200, substrateportion 3270 can be coupled to a voltage, for example, approximately 20volts.

FIG. 33 shows memory device 3200 after material 3301 has been formed intrenches 3211, 3212, and 3213 (FIG. 32). Forming material 3301 caninclude depositing dielectric material (e.g., silicon oxide) oversubstrate 3201 to fill trenches 3211, 3212, and 3213. Then, a topportion of the dielectric material can be removed by, for example, CMP.

FIG. 34 shows memory device 3200 after material 3401 and trenches 3411,3412, and 3413, and device structures 3460 have been formed. Formingmaterial 3401 can include depositing dielectric material (e.g., siliconoxide, or silicon nitride) over substrate 3201 and material 3301.Forming trenches 3411, 3412, and 3413 can include removing (e.g.,etching) portions of substrate 3201, material 3301, and material 3401.Device structures 3460 are formed as a result of the formation oftrenches 3411, 3412, and 3413.

FIG. 35 shows memory device 3200 after a formation of doped regions3501, material 3502, and select lines 3561, 3562, and 3563. Formingdoped regions 3501 can include inserting (e.g., implanting) n-typeimpurities into selective portions of substrate portion 3271. Material3502 (e.g., silicon oxide) can be formed on both sides of each devicestructure 3460 to electrically isolate select lines 3561, 3562, and 3563from device structures 3460. Materials of select lines 3561, 3562, and3563 can include one or more conductive materials, such as one or moremetals, alloys, other conductive materials, or a combination thereof.Select lines 3561, 3562, and 3563 can correspond to select lines 261,262, and 263 of memory device 3000 of FIG. 30.

FIG. 36 shows memory device 3200 after material 3601 have been formed intrenches 3411, 3412, and 3413. Forming material 3601 can includedepositing dielectric material (e.g., silicon dioxide) to fill trenches3411, 3412, and 3413. Then, a top portion of the dielectric material canbe removed by, for example, etching back the conductive material or byCMP, stopping at substrate portion 3270.

FIG. 37 shows memory device 3200 after grooves 3701 have been formed byremoving (e.g., by wet etching) a top portion of the material used toform select lines 3561, 3562, and 3563. Alternatively, forming grooves3701 can be omitted.

FIG. 38 shows memory device 3200 after other components have beenformed. The processes for forming the components of memory device 3200in FIG. 38 can include similar or identical processes for forming thecomponent of memory device 500 described above with reference to FIG. 10through FIG. 29. For example, control gates 3821, 3822, and 3823 of FIG.38 can be formed using processes similar to or identical to those offorming control gates 1221, 1222, and 1223 of memory device 500described above with described above with reference to FIG. 5 throughFIG. 29. Data lines 3851, 3852, and 3853 of FIG. 38, can correspond todata lines 251, 252, and 253 of FIG. 30 and FIG. 31. As shown in FIG.38, memory device 3200 can include memory cells 3810, 3811, and 3812,which can be formed using processes similar to or identical to those offorming memory cells 2910, 2911, and 2912 of memory device 500 describedabove with reference to FIG. 5 through FIG. 29.

One or more embodiments described herein include a memory device andmethods of forming the memory device. One such memory device can includea first group of memory cells, each cell of the first group being formedin a respective cavity of a first control gate located in one devicelevel of the memory device. The memory device also can include a secondgroup of memory cells, each cell of the second group being formed in acavity of in a second control gate located in another device level ofthe memory device. Additional apparatus and methods are described. Otherembodiments including additional apparatus and methods are describedabove with reference to FIG. 1 through FIG. 38.

The illustrations of apparatus such as memory devices 100, 200, 500,3000, and 3200, and memory cells 210, 211, 212, 2910, 2911, 2912, 3010,3811, and 3812 are intended to provide a general understanding of thestructure of various embodiments and not a complete description of allthe elements and features of the apparatus that might make use of thestructures described herein.

The apparatus of various embodiments may include or be included inelectronic circuitry used in high-speed computers, communication andsignal processing circuitry, memory modules, portable memory storagedevices (e.g., thumb drives), single or multi-processor modules, singleor multiple embedded processors, multi-core processors, data switches,and application-specific modules including multilayer, multi-chipmodules. Such apparatus may further be included as sub-components withina variety of electronic systems, such as televisions, cellulartelephones, personal computers (e.g., laptop computers, desktopcomputers, handheld computers, tablet computers, etc.), workstations,radios, video players, audio players (e.g., MP3 (Motion Picture ExpertsGroup, Audio Layer 3) players), vehicles, medical devices (e.g., heartmonitor, blood pressure monitor, etc.), set top boxes, and others.

The above description and the drawings illustrate some embodiments ofthe invention to enable those skilled in the art to practice theembodiments of the invention. Other embodiments may incorporatestructural, logical, electrical, process, and other changes. Examplesmerely typify possible variations. Portions and features of someembodiments may be included in, or substituted for, those of others.Many other embodiments will be apparent to those of skill in the artupon studying and understanding the above description.

The Abstract is provided to comply with 37 C.F.R. §1.72(b) requiring anabstract that will allow the reader to quickly ascertain the nature andgist of the technical disclosure. The Abstract of the Disclosure issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims.

What is claimed is:
 1. An apparatus comprising: a substrate of a memorydevice; a plurality of first memory cells located in a first devicelevel of the memory device over the substrate; a plurality of secondmemory cells located in a second device level of the memory device overthe first device level and over the substrate, wherein the first devicelevel is different from the second device level; a first control gateformed in the first device level, the first control gate to controlaccess to the first memory cells, wherein each of the first memory cellsincludes a memory element formed in a cavity of the first control gate;a second control gate formed in the second device level, the secondcontrol gate to control access to the second memory cells, wherein eachof the second memory cells includes a memory element formed in a cavityof the second control gate; and data lines configured to be selectivelycoupled to a common source and the memory cells through conductivematerial.
 2. The apparatus of claim 1, wherein the first and secondmemory cells include multiple memory cells arranged in a first directionand multiple memory cells arranged in a second direction, the conductivematerial extending through the first and second memory cells in a thirddirection, the third direction being substantially perpendicular to thefirst and second directions.
 3. The apparatus of claim 2, wherein thecommon source is formed over a substrate of the memory device, such thatthe common source is between the first and second memory cells and thesubstrate to allow electrons from the memory element of at least one ofthe first and second memory cells to move to the common source during anerase operation.
 4. The apparatus of claim 1, wherein the first memorycells are substantially vertically aligned with the second memory cells.5. The apparatus of claim 1, wherein the memory element of each of thefirst memory cells is substantially vertically aligned with the memoryelement of one of the second memory cells.
 6. The apparatus of claim 1,further comprising transistors to selectively couple the first andsecond memory cells to the data lines associated with the first andsecond memory cells during a memory operation of the memory device,wherein at least one of the transistors comprises a double-gate.
 7. Theapparatus of claim 1, further comprising transistors to selectivelycouple the first and second memory cells to the data lines associatedwith the first and second memory cells during a memory operation of thememory device, wherein at least one of the transistors comprises asurrounded gate.
 8. An apparatus comprising: a plurality of first memorycells located in a first device level of a memory device; a plurality ofsecond memory cells located in a second device level of the memorydevice; a first control gate formed in the first device level, the firstcontrol gate to control access to the first memory cells, wherein eachof the first memory cells includes a memory element formed in a cavityof the first control gate; a second control gate formed in the seconddevice level, the second control gate to control access to the secondmemory cells, wherein each of the second memory cells includes a memoryelement formed in a cavity of the second control gate, wherein the firstand second memory cells include multiple memory cells arranged in afirst direction and multiple memory cells arranged in a seconddirection; a common source; and data lines configured to be selectivelycoupled to the common source and the first and second memory cellsthrough conductive material, the conductive material extending throughthe first and second memory cells in a third direction, the thirddirection being substantially perpendicular to the first and seconddirections, wherein the common source is formed over a substrate of thememory device, such that the first and second memory cells are betweenthe common source and the substrate.
 9. An apparatus comprising: a firstnon-volatile memory cell including a first memory element, the firstmemory element having a ring shape, the first memory element located ina first device level of a memory device; a second non-volatile memorycell including a second memory element, the second memory element havinga ring shape, the second memory element located in a second device levelof the memory device, wherein the first device level is different fromthe second device level; a conductive material extending through thefirst and second memory elements; and a data line configured to beselectively coupled to a common source and the first and second memorycells through the conductive material.
 10. The apparatus of claim 9,further comprising: a first additional conductive material configured tooperate as a control gate to access the first memory cell, wherein thefirst memory element and the first additional conductive material arelocated in the first device level of the memory device; and a secondadditional conductive material configured to operate as a control gateto access the second memory cell, wherein the second memory element andthe second additional conductive material are located in the seconddevice level of the memory device.
 11. The apparatus of claim 10,wherein each of the first and second memory cells further includes afirst dielectric between the respective memory element and theconductive material.
 12. The apparatus of claim 11, wherein each of thefirst and second memory cells further includes a second dielectricbetween the respective memory element and the respective additionalconductive material.
 13. The apparatus of claim 9, wherein the data lineis located between the substrate and the first memory cell.
 14. Theapparatus of claim 9, wherein the first and second memory cells arelocated between the substrate and the data line.
 15. An apparatuscomprising: a substrate of a memory device; a first conductive materiallocated in a first device level of the memory device over the substrate,the first conductive material including a first cavity, the first cavityhaving a first sidewall; a second conductive material located in asecond device level of the memory device over the first device level andover the substrate, the second conductive material including a secondcavity, the second cavity having a second sidewall, wherein the firstdevice level is different from the second device level; a firstdielectric formed on the first sidewall and the second sidewall; a firstmemory element located in the first cavity and electrically isolatedfrom the first conductive material by a first portion of the firstdielectric; a second memory element located in the second cavity andelectrically isolated from the second conductive material by a secondportion of the first dielectric; a second dielectric formed on a side ofthe first memory element and on a side of the second memory element; anda conductive channel extending from the first device level to the seconddevice level and facing the first and second memory elements, such thatthe conductive channel is electrically isolated from the first andsecond memory elements by at least a respective portion of the seconddielectric.
 16. The apparatus of claim 15, wherein the first and secondmemory elements comprise polysilicon.
 17. The apparatus of claim 15,wherein the first and second memory elements comprise a dielectricmaterial.
 18. The apparatus of claim 17, wherein the dielectric materialcomprises silicon nitride.
 19. The apparatus of claim 15, furthercomprising dielectric material between the first and second conductivematerials.
 20. The apparatus of claim 15, further comprising: a dataline configured to be selectively coupled to the conductive channel,wherein the first and second memory elements are located between thedata line and the substrate.
 21. An apparatus comprising: a firstconductive material located in a first device level of a memory device,the first conductive material including a first cavity, the first cavityhaving a first sidewall; a second conductive material located in asecond device level of the memory device, the second conductive materialincluding a second cavity, the second cavity having a second sidewall; afirst dielectric formed on the first sidewall and the second sidewall; afirst memory element located in the first cavity and electricallyisolated from the first conductive material by a first portion of thefirst dielectric; a second memory element located in the second cavityand electrically isolated from the second conductive material by asecond portion of the first dielectric; a second dielectric formed on aside of the first memory element and on a side of the second memoryelement; a conductive channel extending from the first device level tothe second device level and facing the first and second memory elements,such that the conductive channel is electrically isolated from the firstand second memory elements by at least a respective portion of thesecond dielectric; a substrate; and a data line configured to beselectively coupled to the conductive channel, wherein the data line islocated between the second conductive material and the substrate.